How to use interface type as a model in mgo (Go)?

Question

Suppose you have a workflow that consists of multiple embedded nodes of different types. Since nodes are of different types, I thought of using Golang interfaces here and ca

Answer 1

You cannot use an interface in a document for the reason you noted. The decoder has no information about the type to create.

One way to handle this is to define a struct to hold the type information:

type NodeWithType struct {
   Node Node `bson:"-"`
   Type string
}

type Workflow struct {
   CreatedAt time.Time
   StartedAt time.Time
   CreatedBy string
   Nodes []NodeWithType
}

Implement the SetBSON function on this type. This function should decode the type string, create a value of the correct type based on that string and unmarshal to that value.

func (nt *NodeWithType) SetBSON(r bson.Raw) error {
}